Process and apparatus for coating



May 3, 1932. R. P. CARLTON J PROCESS AND APPARATUS FOR COATING Filed Nov. 10, 1928 Patented May 3, 1932 UNITED STATES PATENT OFFICE RICHARD P. CARLTON, OF ST. PAUL, MINNESOTA, ASSIGNOR TO MINNESOTA MINING &; MANUFACTURING COMPANY, OF ST. PAUL, MINNESOTA, A CORPORATION OF MINNESOTA PROCESS AND APPARATUS FOR COATING Application filed November 10, 1928. Serial No. 318,429.

This invention relates in general to an improved method or process and improved apparatus for carrying out such process for coating flexible materials and more particularly relates to improved process and apparatus for manufacturing flexible abrasive articles such, for example, as sandpaper, emery paper or cloth, and the like.

While the invention is described and illustrated as a process and apparatus for manufacturing sandpaper, it will be understood that it finds utility in the manufacture of other articles and, may, therefore, be adapted to a wide field of utility.

In the customary manner of manufacturing coated flexible abrasive articles, a film of adhesive material is applied to a moving web such for example, as paper, cloth or the like by passing the web through a set of squeeze rollers, the lower roller of which runs in a path of adhesive, the web is then passed under a hopper and a grit or layer of abrasive material is applied to the adhesive side ofthe web from this hopper. To obtain complete coating with the grit, it is necessary that a small excess of grit be applied and. from the hopper the web passes around the roller and over a suction drum, the excess of grit building up around the roller and beyond a certain point the grit will work out at the edges of the web. The amount of grit picked up by the web depends on the thickness of the.

adhesive coat, the wetting properties of the adhesive and the character of the surface of the grain and the tension in the moving web. The tension tends to force the grain or abrasi've material into the adhesive and results in the adhesive being turned over and thus losing some of its abrasive qualities in the final product.

The principal objects of this invention reside in the provision of an improved process wherein the web, after being coated, is maintained free of external pressure on the grit coated side of the sheet while in a wet state andwherein the method and apparatus permit of the proper quantity of adhesive, and abrasive grit being a plied to the coating process to ive a nice balance in the final product an thereby producing a freer cutting, sharper material and resulting in a better bond between the adhesive, backing, that is, the web, and the grit.

It will be understood'by, those skilled in the art that the best cutting properties are obtained in a coat of abrasive sheet when there is sufficient spacing between the particles of grit to allow the grit in some respects to clean itself in use. In other words, it is desirable to avoid too dense a grit layer.

The present invention permits of an equal production rate to that of the prior methods, and prevents the grit from coming in contact with any rollers before the adhesive is dry and thereby avoids turning of the grit and dulling of the finished product.

With the foregoing in View, the principal objects and advantages of this invention reside in the provision of an improved process and apparatus which produce a sharper coated sheet by eliminating contact between any rollers in the conveying mechanism and the grit when the sheet is still in a wet state; the process and apparatus including the provision of a sharper coated sheet which is less dense and in which the layer of grit is not unduly pressed into the adhesive and submerged; the process and apparatus which permits of an improved control of the quantity of adhesive and of grit so as to increase or decreasethe thickness of one or both of the layers of adhesive and grit; and the provision of an improved process and apparatus of the character referred to which permits of the Web or backing being pretreated with waterproofing or other sizing material in the same operation and without materially changing the rate of production, that is, in other words, the rate of production by this invention is the same, if not more rapid than the prior methods known to me.

The foregoing and such other objects and advantages as may appear or be pointed out as this description proceeds may be attained in a structure such for example, as that illustrated in the accompanying drawings in which Figure l is a schematic view in side elevation of an apparatus incorporating the improvements of this invention and Figure 2 is a similar view of an alternative form of the invention.

The improved process of this invention includes the step of conveying the paper or cloth web at a substantially continuous speed to be determined as best for production purposes and depending upon the rate of production desired, this web being coated on one side with an adhesive layer and a grit being applied to the adhesive layer substantially immediately thereafter, the web being continuously moved during these steps. The web is preferably moved in a plane which will permit of a ready retension of the grit, an excess quantity thereof being applied evenly over the whole surface of the web so that distributing rollers for the grit coated surface may be dispensed with. Within a predetermined time after depositing the grit on the adhesive I change the plane of movement of the web, preferably disposing the same at an angle so that the excess grit, which has not adhered in the period of time between a deposition and change in angular movement of the web, will drop off the web by gravity and this grit will then be recovered for further use. The web is then festooned, care being taken to maintain the grit and adhesive coated side thereof out of contact with any objects, that is, free of any external pressure. In other words, all of the tensioning done on the web and paper is applied to the side thereof opposite to that carrying the grit and adhesive. In some instances, it is desirable to pretreat the web, such for example, where a back-sizing or waterproofing coat is desirable or wherein a treatment of both surfaces of the sheet is required to obtain better results in the final product. This step may be carried out prior to the application of the main bonding adhesive and the application to the grit without interfering with the normal carrying out of the process in the manner above des ribed.

For the purpose of carrying out the simple process of applyingthe adhesive and grit, I provide an apparatus w ich may be essentially that shown in Eigure 1.

In Figure 1, the floor 5 is shown on which the apparatus of the invention may be mounted, and it will be understood that the various structural elements of the apparatus will be suitably supported from frame work not shown.

A paper cloth roll is indicated at 6 from which the web 7 is taken ofi around idler rollers 8, 9 and 10 arranged so that the web will pass beneath a container 11 having a liquid adhesive therein, and adhesive a plying roller 12 having a portion thereof su merged in the adhesive in said container 11. The web 7 is then trained over a roller 13 disposed above the adhesive applying roller 12 so that one side of the web receives 9.

of adhesive. As the web passes over the top of the roller 13 and over an auxiliary roller 14, the adhesive coated side thereof will be pressed upwardly. The web is passed over an adjustable idler roller 15 and disposed in a substantially horizontal plane beneath a hopper 16, having gates 17, the hopper containing pulverulent abrasive material, such for example, as sand, garnet, or the like which is permitted to flow in a steady stream of predetremined rate and quantity through the gates 17 to form a layer on the adhesive coated side of the web 7 immediately adjacent and below said hopper. The grit thus disposed is in excess of that finally required in the finished product and a quantity of the grit will adhere to the adhesive, the remainder thereof being loose, as the web passes over the idler roller 15, will fall off the web and into an auxiliary receiving hopper 18. The web is purposely disposed below the roller 15 so that the force of gravity will readily act on the excess grit and cause it to be deposited in the hopper 18. The web is then carried over idler rollers 19, 20, and 21 and over the feeding roller 22 to the usual festooning rack not shown, wherein the web is formed in loops as indicated at 23 for drying.

The roller 15 is mounted for rotation on an adjustable arm 24 operated in any suitable manner to cause the roller to move laterally with respect to the hopper and thus increases or decreases the distance between the point at which the web is deflected in its angu-- lar direction of movement and the point at which the web initially receives the grit. It will be understood that the time interval elapsing between deposition of the grit and which in the angular direction of movement of the web will determine the quantity of grit which will be retained by the adhesive. Of course, this is further variable by control of the quantity of grit permitted to fall upon the adhesive coat and by variation of the thickness of the adhesive coat and its viscosity. It will further be observed that subsequently to the deposition of the adhesive and grit no external pressure is applied directly to the grit coated surface of the web. That is, the web passes over the rollers 15, 19, 20, 21 and 22 and is not subjected at any point before festooning, to pressure from the outside. The tension which is maintained on the web throughout its entire. run is applied, subsequently to deposition of the adhesive and grit, to the surface of the web opposite to that containing the abrasive coat.

It will thus be seen that upsetting or turning of the grit owing to the application of pressure or. squeeze rollers thereto, is prevented in the inethod and apparatus herein described. A nicer and more accurate regulation of the grades of finished product is possible in the present invention as the grade of paper, that is, the coarseness of the grit and the flexibility thereof, etc., are determined by the amount of adhesive deposited, its viscosity, the amount of grit permitted to be deposited on the web, and the time elapsing between the deposition of the grit and removalof the excess quantity thereof. By regulation of any one or all of these factors a change in the finished abrasive product may be accomplished and done so within much finer steps than heretofore possible.

The apparatus shown schematically in Figure 2 is substantially like that shown in Figure 1, with the exception that the web indirated at 711 has been passed through a pretreating apparatus not shown and, therefore, must be trained over idler rollers 25, 26, 27, 28, 29, 30 and 31 before applying the bonding adhesive from the adhesive roller 32. From this point on, the coating of the web with adhesive and grit is substantially the same as that shown in Figure 1. Thereason for the long run of the web between the pretreating apparatus and the grit and adhesive applying apparatus is to permit of a partial setting, if not an entire setting, of the pretreating coat or coats. From the adhesive roll 32 the web passes over the rollers 13a, 14a, and 15a beneath the hopper 16w similarly to Fig. 1 and is then conducted over suitable idler rollers ,and the main feed roller 22a whereupon it is festooned as indicated at 23a.

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent is 1. In an apparatus of the character described, in combination, means for continuously feeding a flexible web, means for applying an adhesive to one surface thereof, means for depositing a grit or abrasive on said adhesive side of the web, means including an angularly displaceable member for changing the direction of travel angularly of the web to a degree sufficient for removing a portion of the grit, and means for varying the position of the angularly displaceable member.

2. The method of making an abrasive article, which includes as steps thereof, applying an adhesive coating to a moving backing, and while said adhesive is still plastic applying a grit thereto, then changing the direction of travel of the backing to cause some of the grit to remove itself from the adhesive, and varying the period of time elapsing between application of the grit and change in direction of travel of the backing, for varying the thickness of the coating of grit retained by the adhesive.

3. The method of making an abrasive article, which includes as steps thereof, applying an adhesive coating to a moving backing, and while said adhesive is still plastic applying a grit thereto, then changing the direction of travel of the backing to cause some of the grit to remove itself from the adhesive,

and varying the period of time elapsing between application of the grit and change in direction of travel of the backing, forvarying the thickness of the coating of grit retained by the adhesive and maintaining the grit carrying side of said backing free of external pressure until set.

4. In an apparatus of the character described, in combination, a hopper depositing a layer of pulverulcnt material on a traveling web having an adhesive coated surface, a roller over which said web passes for changing the direction of angular movement thereof, and means for varying the position of said roller for controlling the time elapsing between deposition of the pulverulent material and change in direction of movement of the Web for regulating the thickness of the grit coating, said roller being laterally displaceable with respect to said hopper.

5. In an apparatus of the character described, in combination, means for feeding a flexible backing web, means for applying an adhesive to one surface thereof, means for depositing a grit or abrasive on said adhesive side of the web, means including a displaceable tensioning member over which the backing is trained for changing the direction of travel angularly of said web to a degree sufficient for removing a portion of the grit carried thereby, and means for varying the position of said tensioning member.

6. In an apparatus of the character described, in combination, means for feeding a flexible backing web, means for applying an adhesive to one surface thereof, means for depositing a grit or abrasive on said adhesive side of the web, means including a displaceable tensioning member over which the backing is trained for changing the direction of travel angularly of said web to a degree sufficient for removing a portion of the grit carried thereby, said tensioning member being movable toward and away from said grit depositing means for varying the interval of time elapsing between deposition of grit and angular change in direction of movement of the web, and means for moving said tensioning member.

7. In an apparatus of the character described, in combination, means for feeding a flexible backing web, means for applying an adhesive to one surface thereof, means for depositing a grit or abrasive on said adhesive side of the web, means including a displaceable tensioning member over which the backing is trained for changing the direction of travel angularly of said web to a degree sufficient for removing a portion of the grit carried thereby, and means for varying the position of said tensioning member, and means for maintaining the grit coated side of the web out of contact with external pressure enroute to the place of, and until drying.

8. In the method of making an abrasive article, the steps which comprise applying an adhesive upon one side of a backin material and while the adhesive is plastic, epositing a rit or layer of abrasive garticles upon the ad esive coated side of sai backing, and diverting the abrasive from the adhesive coated side in a direction away from the adhesive for removing the excess of said particles while the adhesive is still plastic, and continuously feeding the backing so prepared without external pressure upon the abrasive coated surface from the point of deposition of rit until the adhesive is set.

testimony whereof, I have hereunto signed my name.

RICHARD P. CARLTON. 

